The present invention relates to limitation of the amounts of aerodynamic drag experienced by railway cars, and particularly to limitation of aerodynamic drag on multi-unit railcars configured for carrying intermodal cargo containers stacked in two tiers.
Railcars have been developed in recent years which can carry standard intermodal cargo containers stacked in two tiers, one above the other, without exceeding the maximum height limitations of railroad rights-of-way. Use of such cars makes long-haul transportation of such cargo containers by rail more economical than by tractor-trailer truck combination over the highways, because of the greater fuel economy resulting from using railway locomotives instead of a greater number of truck tractor units. Nevertheless, it is desired to reduce further the fuel requirements for hauling such cargo containers by rail.
Container cars have been designed recently which include several container-carrying units interconnected with one another by articulating joints each having a single two-axle truck with an end of each of two adjacent car units being pivotally supported by that truck. Such construction saves material and, consequently, reduces costs for construction of the multi-unit car. It also reduces the amount of fuel required to haul a given number of cargo containers, assuming that the multi-unit car can be fully loaded.
Particularly at higher railway train speeds, aerodynamic drag is a significant factor in the amount of fuel consumed in hauling a train. In the case of railway cars having a large frontal surface which is predominantly flat and perpendicular to the length of the car, as is the case when a cargo container is located in an upper tier of such a multi-unit container car, a significant amount of aerodynamic drag results from turbulence in the gaps between the ends of containers carried on adjacent multi-unit cars and on the adjacent units of a multi-unit car.
While it is to be expected that completely closing the gaps between cars would improve the aerodynamic characteristics of a train, the cost of closing such gaps would be prohibitive. Additionally, while the presence of streamlining structures between units of a multi-unit container car and between adjacent multi-unit cars would improve the aerodynamic characteristics of a train if the cargo container-carrying cars are fully loaded, the presence of such structures would cause an undesirably high amount of aerodynamic drag when container cars are hauled without being fully loaded, unless such devices are collapsible. Collapsible construction would, of course, add to the cost of such streamlining devices.
Apparently, a major cause of aerodynamic drag associated with container cars is the formation of large vortices between adjacent cars or car units. Larger gaps admit formation of larger vortices, containing larger volumes of air being moved turbulently, and thus absorbing larger amounts of energy which must be replaced by the locomotive in order to keep the train moving at a particular rate.
A separate factor which must be considered particularly with respect to design of cargo container-carrying railcars is that some of the equipment used to place cargo containers on such cars or remove containers from such cars requires certain amounts of clearance at the ends of cars when handling containers shorter than the usual forty-foot-long containers. Container-loading equipment used in many rail yards extends longitudinally several feet beyond each end of a twenty foot container being lifted, and so clearance for the loader must be provided at each end of a car into which such twenty foot containers are being loaded. Such a loader clearance, however, is not consistent with the presence of a fixed streamlined body filling all of the available space between cargo containers in adjacent cars (or adjacent units of the same car).
Additionally, various clearances must be provided for the trucks, handbrake equipment, draft gear, and hoses, extending between adjacent cars. As a result, useful streamlining structures extending longitudinally to fill all of the spaces between adjacent cars of a freight train are too expensive, too complex, and too likely to be damaged.
Wiley U.S. Pat. No. 4,257,640 discloses a single, vertical, longitudinally-extending, located panel extending between the cab of a truck and the forward end of a cargo-containing portion of such a truck. Wiley also discloses a laterally offset location for such a single panel. In the case of railway cars, however, a centrally located panel of the type disclosed by Wiley would need to be interrupted by a large amount of open space, because of the required clearances for trucks, couplings, and related portions of a railcar. It would still leave space available for the formation of significantly large vortices and zones of turbulent air movement between adjacent cars.
What is needed, therefore, are relatively simple structures for improving the aerodynamic characteristics of railway container cars. Such devices should be sturdy, but inexpensive to construct, light in weight, and effective for improving the aerodynamic characteristics of fully loaded container cars, yet low in drag when such cars are hauled in an empty condition. They should not interfere with loading of cars configured for carrying short containers, and should not interfere with the ability of such cars to negotiate curves in the railway tracks. Furthermore, such devices are needed both for the relatively small gaps between units of a multi-unit car and for the relatively large gaps between the ends of adjacent cars coupled together.